1. Field of the Invention
The invention relates to heating mechanisms for process chambers, and particularly, to heating mechanisms for chemical vapor deposition chambers.
2. Description of Related Art
Chemical vapor deposition (CVD) is a process for depositing various types of films on substrates and is used extensively in the manufacture of semiconductor-based integrated circuits such as, for example, the processing of semiconductor wafers (wafers) to form individual integrated circuit devices. In typical CVD processing, a wafer or wafers are placed in a deposition or reaction chamber and reactant gasses are introduced into the chamber that are decomposed and reacted at a heated surface to form a thin film on the wafer or wafers.
A CVD reactor vessel adds coatings to wafers using a multi-zone resistive heater (heater) to react the coating chemistry once applied to a wafer surface. The heater includes at least two resistive heating rods disposed within a tube to contact a spiral heater coil (coil) embedded within a heater disk (disk). The distinct heating rods are not equadistantly centered about the tube centerline nor the coil. Instead they are offset, the result being that areas of the heating disk can have a wide range of temperatures provided by varying the electrical power applied to the individual heating rods. A specially designed surface (susceptor) exists on one side of the heating disk upon which is supported the wafer. The wafer is heated conductively by heat transferred from the heating coil to the susceptor. Upon completion of the deposition of the film onto the wafer, the process gasses are removed, the reaction chamber purged with cleaning chemicals and inert gasses, and the wafer removed.
Initially at assembly, an interior volume of the heater assembly is exposed to atmosphere. Once the heater is assembled, atmosphere will remain contained within. Oxygen in the atmosphere that is contained within the heater assembly will attack the heater components at temperatures above 700xc2x0 C. As a result, the mechanical strength of the heater components will degrade with use and the heater components will have to be replaced at a cost in parts, labor, and down time for the reactor vessel.
A wafer processing method, comprising processing a wafer in a reaction chamber comprising a heater having an interior space; heating the reaction chamber with the heater, purging an inert gas into the heater interior space, and venting the inert gas.